The present invention relates generally to the blow molding of thermoplastic material and, more particularly, to a method of and apparatus for blow molding plastic articles having inserts permanently affixed thereto while maintaining the integrity of the wall surfaces of the article.
In molded plastic articles, such as storage tanks, containers and the like, it is sometimes desirable to provide inserts, such as fittings, sockets, nuts and the like, in the walls of these plastic articles for attaching the same to other support structure or for connecting valves, hose and conduit couplings or other members thereto. Conventionally, these inserts are fitted into the plastic article after it has been formed by pinning the insert therein or by employing separable fasteners to secure the inserts in place. Not only is this a time-consuming and expensive procedure requiring a number of parts, but the wall surfaces of the plastic article are necessarily punctured and pierced, thereby interrupting the integrity of such wall surfaces. Providing and maintaining a fluid-tight seal about the insert presents a problem. Also, a problem is encountered in rigidly affixing these inserts to the wall surfaces in order to preclude displacement or removal of such inserts from their original positions.